You only need three chemicals to open a pool.

Yes, and it’s simpler than the pool store wants you to think.

The three essentials are: shock (non-chlorine or chlorine), algaecide, and a stabilizer (cyanuric acid) if your levels are low. That’s it. You also need to test and adjust pH and alkalinity before anything else, but those aren’t “opening chemicals” — they’re just water balance basics.

Shock kills whatever grew over winter. Algaecide stops new algae from taking hold. Stabilizer protects chlorine from burning off in the sun. If you already have good CYA from last year, skip the stabilizer. Don’t buy “opening kits” with six bottles of mystery goo — most of it is overpriced water.

The pool store will try to sell you a cart full. Ignore them.